The invention concerns a hydraulic system, comprising at least one hydraulic drive means, a conduit system connected to the hydraulic drive means for conveying hydraulic liquid to and from the hydraulic drive means, where the conduit system comprises a conduit circuit containing hydraulic liquid, connected to the hydraulic drive means, a pump for generating a flow of hydraulic fluid in the conduit system and a motor to power the pump.
Hydraulic systems of the type mentioned in the introduction are known and are used in a large number of different technical fields. For example one or more hydraulic cylinders in such a hydraulic system can be used in an industrial truck to control its lifting movements, i.e. control of the truck's handling of a load including raising and lowering the load, and even horizontal movements of the load. Further examples of technical fields where the said type of hydraulic system can be applied include all sorts of working machines, such as digging machines for control of the digging machine's digging movements, tool machines, robots and such for example.
In hydraulic systems of the said type the motor's power is transformed to hydraulic power in the pump, whereby the flow of hydraulic liquid in the conduit system generated by the pump is usually distributed to the at least one hydraulic drive means via one or more valves. By controlling the flow to at least one hydraulic drive means via valves, such as throttle valves or directional valves for example, the hydraulic drive means is thereby controlled. However, a disadvantage with such a hydraulic system is that heat is generated on controlling the flow with throttle valves, which has a negative effect on the components comprised in the system and therefore the installation of expensive cooling systems requires in certain cases. The generation of heat also involves a disadvantageous energy loss.